A fluid dynamic bearing device rotatably supports a rotating member by a lubrication film of a fluid created in a bearing clearance between a fixed member and the rotating member. This type of bearing device has characteristics of high-speed rotation, high rotation accuracy, low noise and the like, and is preferably used as a bearing device for a motor mounted on various types of electric equipment including information equipment, more specifically, as a bearing device for a spindle motor of a disk drive in a magnetic disk device such as HDD, an optical disk device such as CD-ROM, CD-R/RW, DVD-ROM/RAM and the like, a magnetic optical disk device such as MD, MO and the like, or as a bearing device for a motor such as a polygon scanner motor of a laser beam printer (LBP), a color wheel motor of a projector and a fan motor.
For example, in a fluid dynamic bearing device incorporated in a spindle motor of a disk drive device such as HDD, there is known one in which both a radial bearing part supporting a shaft member in a radial direction and a thrust bearing part supporting in a thrust direction are made of dynamic pressure bearings. As the radial bearing part in this type of the fluid dynamic bearing device (dynamic pressure bearing device), there is known one in which dynamic pressure grooves as a dynamic pressure generating part that create a dynamic pressure action of a fluid in a bearing clearance are formed, for example, in either of an inner circumferential surface of a bearing sleeve making up the fixed member, and an outer circumferential surface of a shaft member making up the rotating member, and a radial bearing clearance is formed between both the surfaces (e.g., refer to Patent Document 1).
Moreover, since a disk drive device such as HDD is used in a relatively wide temperature range, a lubricant fluid having a low evaporation rate and a low viscosity is preferable for a fluid dynamic bearing device used in a spindle motor of the disk drive device. For example, an ester-based lubricating oil is used (e.g., refer to Patent Document 2).
This type of fluid dynamic bearing device is made up of a plurality of components including, for example, a shaft member, a bearing sleeve, a housing and a seal member, and, it is considered that among these, the components such as the housing and the sealing member are molded using a resin material in view of moldability and low cost (e.g., refer to Patent Documents 3 and 4). Moreover, there is proposed a resin molding in which carbon fibers are compounded into a resin material as a filler for enhancing reinforcement effects and dimensional stability of the resin molding (e.g., Patent Document 5)    [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-291648    [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-172336    [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-314534    [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-265119    [Patent Document 5] Japanese Patent Application Laid-Open No. 2006-46431